Imaging methods utilizing electromagnetic radiation can be divided into two groups: radioscopic methods and tomographic methods. In traditional radioscopy, the radiation source, the object to be imaged and the radiation detector, e.g., an x-ray film, are stationary with respect to one another during the imaging session. Imaging methods in which a narrow beam is moved over the object to be imaged are also known.
Tomographic methods can be divided into linear (i.e. planar) tomographic methods and complex motion or spiral tomographic methods. In linear tomographic imaging, the radiation source and the radiation detector are moved with respect to one another in a controlled manner. That is, the radiation source and the radiation detector are rotated around a vertical axis passing through the object to be imaged so that the radiation beam from the radiation source passes through the object to be imaged and is received by the detector, the radiation beam remaining in a single plane. In complex motion tomography, in addition to rotating around the vertical axis passing through the object to be imaged, the radiation source and radiation detector move vertically in opposite directions from one another thereby varying the angle of the radiation beam passing through the object to be imaged. Both methods preferably use a beam which is of the same size as the object to be imaged. Therefore, in complex tomography, the object to be imaged is usually held in place as the radiation source and radiation detector move dependently on one another on opposite sides of the object to be imaged in opposite vertical directions so that the beam penetrates the object at different angles. However, the location at which the beam penetrates the object does not change. These methods provide accurate images of the imaging area in the center of rotation of the beam, whereas the other parts of the object are blurred partially or totally.
There also exist "narrow beam tomography" methods in which a beam considerably narrower than the object to be imaged sweeps across the area to be imaged and the beam is turned with respect to the object to be imaged. In that case, the imaging means (i.e., the radiation source and the radiation detector) must be moved in a controlled manner so that the detector moves in relation to the beam at a lateral velocity which corresponds to the perpendicular sweeping speed of the beam in the area to be imaged multiplied by the ratio of magnification, i.e., by a coefficient which is the ratio of the distance of the beam focus (radiation source) and the distance of the focus from the area to be imaged. Here, the term "detector" refers to a film or the like. In digital imaging, for example, the movement of the detector with respect to the area to be imaged may be replaced with a suitable electrical function, such as a charge transfer on the surface of a semiconductor sensor.
Thus, it is known to move the radiation source and the radiation detector both horizontally and vertically for producing a tomographic effect. Many prior art devices that enable complex motion paths have very massive structures, and thus it may not be possible to move the imaging means rapidly and change its direction due to the limits set by the general physical principles of moving heavy masses and mechanical solutions of the devices. Against this background, it is not easy to develop commercially feasible devices. The present trend is to develop devices which enable the use of the same device for various purposes, i.e., the goal is to be able to use the same device in different tomographic methods and for imaging different projections. When the same device has different imaging modes, investment in imaging sensors based on modem digital technology becomes more profitable, which lowers the threshold of introducing them. Digital technology facilitates a doctors' work since, for example, it not only allows doctors to produce better images than earlier thereby enabling them to make more accurate diagnoses, but it also enables doctors to store the images and manage them in electronic form, together with all of the other documents related to the patient.